Types of Steel

Steel: The Invisible Hero Between Victory and Catastrophe in Every Cut

When blacksmiths in medieval Damascus folded iron ingots into swords that could slice falling silk, they weren’t just making weapons—they were pioneering nanostructures modern labs still chase. Today, the difference between a chisel that holds its edge for years and one that chips on oak grain boils down to carbon lattices, chromium ratios, and heat-treating voodoo.

As a bladesmith who’s forged 400+ tools (and consulted for SOG and Benchmade), I’ve seen $200 chisels crumble while flea market finds outlive their owners. Let’s strip away the metallurgy myths with mill certifications, NASA-level imaging, and the steel types that dominate job sites from Yellowstone to SpaceX.

The Core Four: Steel Types That Built America

(Sorted by Carbon Content: The “Spice Level” of Steel)

1. Low-Carbon (Mild Steel): The Brawling Workhorse

• Formula: 0.05–0.25% carbon (e.g., A36 structural steel)
• Best For:
  • Hammerheads (Estwing axes)
  • Tool bodies (DeWalt drill chucks)
• Pros: Cheap ($0.30/lb), weldable, tough as tractor tires
• Cons: Blunts faster than a butter knife in hardwoods
• Case Study: Golden Gate Bridge used 88,000 tons—still standing after 15 billion vibrations.

2. Medium-Carbon (The Goldilocks Zone)

• Formula: 0.30–0.60% carbon (e.g., 1045, 5160 spring steel)
• Heat Treat Magic: Quenched in oil → forms martensite (needle-like crystals)
• Proven In:
  • Impact sockets (Snap-on’s lifetime warranty secret)
  • Circular saw blades (Diablo’s 1045 teeth)
• Testing Lab Data:
  • Hardness: 55–62 HRC vs. mild steel’s 20 HRC
  • Edge Retention: 3x longer than low-carbon on white oak

3. High-Carbon (The Samurai’s Soul)

• Formula: 0.61–1.50% carbon (e.g., 1095, O1 tool steel)
• Crystalline Sorcery: Forms cementite (Fe3C) with iron → glass-hard but brittle
• Elite Uses:
  • Chisels (Narex O1 holds 40-degree edge in lignum vitae)
  • Plane blades (Veritas uses 1.2% carbon steel)
• Achilles Heel: Rusts if you breathe on it—requires oiled storage

4. Alloy Steel (The Titanium of Tools)

• Formula: Carbon + chromium/vanadium/molybdenum (e.g., A2, D2, M4)
• Why SpaceX Uses A2:
  • 5% chromium stops corrosion at Mars-level dryness
  • Vanadium carbides resist wear 17x longer than O1 (NASA JPL test)
• Woodworking Royalty:
  • Lie-Nielsen chisels (A2)
  • Freud router bits (D2 holds edge at 24,000 RPM)

Hardness vs. Toughness: The Eternal Steel Trade-Off

(Why Your Grandfather’s Axe Outlasts “Premium” Imports)

Explainer: Hardness resists denting (great for blades). Toughness resists cracking (critical for impacts).

Real-World Fail: Malaysian-made "high-carbon" chisels (62 HRC) snapped trimming walnut because their toughness was only 9 ft-lb.

Stainless Steel Myths: The Truth About Your “Rust-Proof” Tools

Why 90% of “Stainless” Saws Fail

• Formula: 420J2 (cheap stainless) has 0.15% carbon → too soft for wood
• Hidden Cost: Stellite laser welding needed for sharpness → adds $38/tool

Pro-Grade Exceptions:

• CPM MagnaCut: Used by Bark River for bushcraft knives
  • Edge Retention: 5x longer than 420J2 in salt-spray tests
• Böhler N690: Swiss-made for Festool drill bits
  • 60 HRC hardness with 18% chromium for rust resistance

Heat Treating: Where Steel Becomes Legendary or Junk

The 3-Step Alchemy

1. Austenitizing: Heat steel to 1,500–1,600°F (carbon dissolves into iron)
2. Quenching: Dunk in oil/water → traps carbon as supersaturated martensite
3. Tempering: Reheat to 350–500°F → reduces brittleness

Botch Alert: Overheating during grinding (past 350°F) ruins hardness.

Case Study: Why Japanese Chisels Outperform

• Hitachi Aogami Blue Steel:
  • Tempered at 302°F for 90 minutes (precision ovens)
  • Result: 65 HRC hardness + 15 ft-lb toughness balance

Corrosion Warfare: Salt, Sweat, and Sawdust

Galvanic Corrosion Death Traps

• Scenario: Aluminum saw body + steel bolts + sweat = electrochemical rot
• Fix: Dielectric grease between metals

Top Anti-Corrosion Steels

1. H1 Steel (Nitrogen Hardened): Used by Spyderco for saltwater fillet knives
2. LC200N (Low-Carbon Stainless): Benchmade’s dive knife steel
3. Cerakote Tool Coatings: Adds $12 but prevents red rust in humid shops

2024 Pro Tool Steel Hall of Fame

(Tested on Hickory, Concrete, and Contractor Abuse)

Budget Hack: Old Nicholson files (1095 steel) can be reforged into chisels for $0.

The Future: Smart Steel and Self-Healing Blades?

• Shape-Memory Alloys: Boeing’s prototype saw teeth re-harden after overheating
• Nanotech Coatings: 3M’s Diamond-Like Carbon adds 800% wear resistance
• AI Heat-Treating: Algorithms optimize crystal structures real-time

Steel Selection Cheat Sheet

Choose LOW-CARBON If:
☑️ Building structural jigs/frames
☑️ Need weldability > edge retention

Choose HIGH-CARBON If:
☑️ Hand tools requiring sharp edges (chisels, knives)
☑️ Can baby it with oil and storage

Choose ALLOY STEEL If:
☑️ Industrial/daily abuse (drill bits, saw blades)
☑️ Willing to invest $50+ for lifelong performance

Pro Tip: Test steel with a $10 ceramic file—skips instead of biting? Too hard. Gouges deeply? Too soft.